Health insurance denial & claim adjustment codes

What health insurance denial code 66 means on your EOB

A Medicare-specific deductible covering the first pints of blood you receive in a calendar year. It is separate from your Part A and Part B deductibles, which is why it can appear unexpectedly on a notice where everything else looks already met.

What usually causes it

• The annual blood deductible has not been met.
• Blood was replaced by donation, which can waive it.
• It was applied in the wrong benefit year.

The documents that decide it

• Your Medicare Summary Notice.
• Whether blood was replaced by donation.
• The service date and benefit year.

What to do next

If blood was replaced by donation, the deductible is typically waived. Confirm with the facility.

This page explains what a code means. It is information, not advice — it does not tell you whether your specific claim should have been paid, and it is not legal, medical, or insurance advice. Your plan documents and your denial notice govern your situation.